computor after 25 min. starts getting hot and realhot by 40min. then it will shut down in 1second from extreme

Clean the inside of your computer, and make sure all of the fans are running.

http://www.bleepingcomputer.com/tutorials/tutorial...

Im guessing that either the exhaust fan went out and/or the cpu fan on top of the heatsink went out. Either of these would cause the computer to overheat very quickly. The hardware is not necessarily junk. Any computer can have a fan fail, which will always result in various forms of overheating.

You should take the case cover off and then turn on the computer. Look at all of the fans you can see. If one or more of them is not spinning then that is most likely the cause of your problem.

Dust and particle build up around critical components can also contribute to overheating. Spraying the internals of your PC with a compressed air canistor should take care of most of the excess dust.

Could be several things one I would open your tower up and clean it out. Two I would make sure your cpu fan is running and not all crudded up. Three I would make sure the cpu fan is thourghly attached to the cpu.

If none of that works I would open the tower up and get a desk fan and put it a foot away and blow it into the computer.

I think have to keep your computer in free space so that air can freely flow in and out. If the problem is not solved, go replace either motherboard or processor fan which is free for any board.

short answer, the hardware is garbage. I assume it's an old desktop? Maybe you can put a fan next to the system to cool it off.

Not enough circulation in the case. Get more fans and more openings.